“Space-Time MMSE Reception for Multi-Satellite Environment”

This paper deals with the introduction of two new schemes of space-time MMSE reception implemented for the forward link of a WCDMA multisatellite UMTS environment and the comparison with other two similar space-time MMSE receiver already presented in the literature. In all this works the so called space-time transmit diversity technique (STTD) has been coupled with the minimum mean square error (MMSE) interference suppression technique. The idea has come from the realization that the diversity gain is limited by a medium-high level of multiple access interference (L. Mucchi et al., 2002, R. Tesi et al., 2001). The proposed schemes can be distinguished by the order in which the space-time processing and the MMSE interference suppression are performed. We named ST-MMSE pre STTD combining if the MMSE filtering is performed before the space-time combining and ST-MMSE post STTD combining if the interference suppression and the space-time combining are jointly processed. A realistic multisatellite UMTS environment has been simulated in order to compare the proposed detectors. Bit error rates have been calculated by mean of Monte Carlo simulations assuming a time-varying satellite channel model. Simulations show that the post-combining scheme gives the best results, but it implies more complexity to the mobile terminal. Anyway, both the proposed ST-MMSE schemes yield significantly better performance than the standard STTD receiver or the conventional RAKE receiver.